The present invention relates to a software-defined optical network and, more particularly, to a software-defined (SD) optical line terminal (OLT) and a software-defined (SD) optical network unit (ONU).
As both architecture and service heterogeneity continues to increase in optical networks, software-defined optics—i.e. on-demand optical hardware re-configurability via software—is becoming an increasingly important tool for managing network complexity and increasing cost-efficiency. This is particularly important in optical access/metro/backhaul networks, where operators increasingly desire to have a “wholesale network” for heterogeneous services, rather than a set of disparate, application-specific platforms. However, in current architectures, both centralized management units and remote end-user transceivers are designed and implemented in a service-specific way. Consequently, leveraging the same expensive fiber access infrastructure for residential, business and mobile backhaul services becomes quite difficult because of both hardware and management (i.e. quality-of-service, latency, etc.) specificity. Moreover, convergence of different types of mobile backhaul services and protocols (e.g. generic digital radio-over-fiber signaling versus Internet Protocol (IP)-based packet transport) onto a single optical infrastructure likewise becomes complex due to differences in optical transceiver structures and capabilities. Software-defined upgrades of both optical transceivers and software-based management/control units is thus an important way to enable cost-efficient hardware re-configurability and, ultimately, heterogeneous service convergence in optical access/metro/backhaul networks.
In previous work, new software-defined optical network element control protocols, such as OpenFlow, for example, have been proposed in the context of core optical networks. In this environment, the goal of such software-defined control is to abstract hardware-related differences between different vendors in a single network, enabling interoperability, centralized management and control, which can both enable rapid introduction of new services and enhance cost-efficiency. Software-defined optical transceiver functionality has also been explored in long-haul core optical networks, as a way to customize physical transceiver parameters (e.g. modulation format, spectral band size, forward error correction coding rate, etc.) in a way that optimizes the performance of each individual point-to-point link. Similar principles have also been proposed and exploited in software-defined radio systems, in which physical transceiver parameters (e.g. spectral occupancy, transmitter power, etc.) can be modified to optimize use of expensive radio frequency (RF) spectrum subject to multiuser interference constraints, for example. However, in all of these cases, heterogeneous service delivery is not a primary target, the underlying physical hardware is designed to have largely fixed functionality and a relatively small set of software-configurable options. Consequently, while operational and control parameters can be tweaked in software, significant physical and higher layer differences cannot be overcome such that the same software-defined optical transceiver and management structure could be used for disparate applications.
We treat the optical transceiver as a “smart phone” and heterogeneous services (e.g. residential, business, various mobile backhaul scenarios) as software-defined applications that can all run on the optical transceiver platform in a software-configurable way. In other words, an optical transceiver design is presented that includes the necessary hardware functionality to execute physical and higher layer requirements for different services, while a software-defined management approach is introduced to decide which of those hardware function blocks will be activated to execute a target function. In other words, each optical transceiver becomes a local software-defined network, where each hardware block is treated as a network element that is locally controlled in software, but in a centralized fashion. The operations and instructions for the local software controller are in turn issued by a global software-based controller (e.g. in the central office or optical line terminal of the access/metro/mobile backhaul (MBH) network.) Specifically, while the global software-defined controller is responsible for deciding what the remote software-defined transceiver should do, the local software-defined controller has the task to decide how this will be done by local control (i.e. enabling, disabling, scheduling, setting operational parameters, etc.) of the hardware elements in the optical transceiver.
The proposed solution strikes an attractive balance between centralization and distribution of processing functionality in a way that enables convergence of heterogeneous services onto a single optical “wholesale” network. For example, by centralizing global control, management and application specificity but distributing physical-layer intelligence, a single set of smart, software-defined optical transceivers can be used for residential, business, MBH, special purpose, etc., services, and software-configured on-demand a posteriori to implement a specific function. In this way, the mass market volumes and cost-efficiency of digital signal processing (DSP)-based network/transceiver upgrades can be used to both reduce network complexity and cost.